Conventional printers, copying machines, and like image forming devices include a paper feeding device that removes, a sheet at a time, printing paper from a stack on a paper feed tray to feed the sheets individually to an image forming section. The paper feeding device employs one of various mechanisms, such as separation claws, friction pads, and gating, to remove printing paper, a sheet at a time, from a paper feed tray. Many other mechanisms have been also developed by which air is blown at printing paper so that individual sheets can be levitated and separated.
An air blowing device that includes an air blowing fan and an air sucking fan is discussed as a type of paper feeding device that blows air for paper separation (see, for example, Patent Document 1). In the paper feeding device of Patent Document 1, the air blowing fan separates printing paper on a paper feed tray by blowing air at the printing paper. The air sucking fan then draws the separated sheet of printing paper onto a paper feeding belt via an air inlet. The air blowing device is enclosed in a shield member provided with the air inlet to block unwanted noise generated by the air blowing device.
Another type of paper feeding device is discussed which reshapes each sheet of printing paper to be drawn onto a transport belt into an arch form to achieve improved printing paper separation (see, for example, Patent Document 2). In the paper feeding device of Patent Document 2, an air blowing fan blows air at printing paper, and an air sucking fan draws the printing paper onto a transport belt via an air sucking duct that has an air sucking port on its bottom wall. The transport belt is curved by a rib standing out of the bottom wall of the air sucking duct so that the printing paper drawn onto the transport belt is reshaped into an arch form. This mechanism provides an air passage between the printing paper drawn onto the transport belt and the printing paper on a paper feed plate.
These paper feeding devices use a single fan as both the air sucking fan and the air blowing fan. Another type of paper feeding device is discussed which includes two fans that are coupled together (see, for example, Patent Documents 3 and 4).
In the paper feeding device of Patent Document 3, the air outlet of one of the fans and the air inlet of the other fan is linked by a coupling passage so that the two fans can suck in air to draw a sheet of printing paper onto a transport belt. The air blown out of the air outlet of the other fan is aimed at a printing paper storage section on which there is provided a paper feed tray. The paper feeding device levitates and separates printing paper by a levitation air blowing mechanism that blows air at a side face of the stack of printing paper on the paper feed tray and a separation air blowing mechanism that blows air at the front of the printing paper drawn onto the transport belt. The air sucking forces of the individual fans are added up by positioning the two fans in series, to generate a sufficient drawing force.
In the media feeding device of Patent Document 4, there is provided air supply means in which the air outlet of an upstream fan is coupled to the air outlet of the downstream fan via a spiral channel. The air supply means blows air to levitate several sheets from the stack of sheets on a sheet tray. Above the stack of sheets is there also provided suction/transport means including a suction fan that sucks in air to draw the sheet levitated from the sheet tray onto a transport belt. The two coupled fans generate high-pressure air to unfailingly separate and levitate sheets.